linux-kernel - Re: [PATCH 0/3] resource: find_next_iomem

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Date:   Mon, 17 Jun 2019 23:44:34 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Nadav Amit <namit@...are.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>, Borislav Petkov <bp@...e.de>,
        Toshi Kani <toshi.kani@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 0/3] resource: find_next_iomem_res() improvements

On Wed, Jun 12, 2019 at 9:59 PM Nadav Amit <namit@...are.com> wrote:
>
> Running some microbenchmarks on dax keeps showing find_next_iomem_res()
> as a place in which significant amount of time is spent. It appears that
> in order to determine the cacheability that is required for the PTE,
> lookup_memtype() is called, and this one traverses the resources list in
> an inefficient manner. This patch-set tries to improve this situation.

Let's just do this lookup once per device, cache that, and replay it
to modified vmf_insert_* routines that trust the caller to already
know the pgprot_values.